mac80211: minstrel_ht: do not sample unsupported rates

ATM minstrel_ht does not check whether a sampling rate is supported.
Unsupported rates attempts can trigger when there are holes in bitfields
of supported MCSes belonging to the same group (e.g many devices are
MCS32 capable without MCS33->39 capable, also we systematically have a
hole for CCK rates).
Drop any attempts to sample unsupported rates, as suggested by Felix.

This is not a problem in minstrel which fills a per STA sample table
with only supported rates (though only at init).

Signed-off-by: Karl Beldan <karl.beldan@rivierawaves.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/rc80211_minstrel_ht.c b/net/mac80211/rc80211_minstrel_ht.c
index e66e9f9fd0dbdf7c58b85c0dc7eb29f59cd2e588..b91655a0d8f090867d1bdb9c8d2de2d5a63f5919 100644 (file)
--- a/net/mac80211/rc80211_minstrel_ht.c
+++ b/net/mac80211/rc80211_minstrel_ht.c
@@ -700,12 +700,16 @@ minstrel_get_sample_rate(struct minstrel_priv *mp, struct minstrel_ht_sta *mi)
        if (!mi->sample_tries)
                return -1;
 
-       mg = &mi->groups[mi->sample_group];
+       sample_group = mi->sample_group;
+       mg = &mi->groups[sample_group];
        sample_idx = sample_table[mg->column][mg->index];
+       minstrel_next_sample_idx(mi);
+
+       if (!(mg->supported & BIT(sample_idx)))
+               return -1;
+
        mr = &mg->rates[sample_idx];
-       sample_group = mi->sample_group;
        sample_idx += sample_group * MCS_GROUP_RATES;
-       minstrel_next_sample_idx(mi);
 
        /*
         * Sampling might add some overhead (RTS, no aggregation)